1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device, and more particularly, to an effective technique for forming a metal oxide film on a process-target substrate.
2. Description of the Related Art
Recently, as semiconductor devices are becoming highly integrated, it is necessary to form a much thinner insulating film during the process of forming semiconductor devices. However, due to the presence of tunnel current when the thickness of the insulating film is small, it is desired that the thickness of the insulating film is optimally reduced while maintaining the thickness of the insulating film at a level where the tunnel effect does not occur, and thus high dielectric constant (high-k) metal oxides such as a hafnium oxide film or a zirconium oxide film are drawing attention as capacitor materials. For example, it is difficult to impose electrical restrictions when a film is formed to a thickness of 1.6 nm by using a silicon oxide. However, an equivalent dielectric constant can be obtained by forming a high-k film to a thickness of 4.5 nm by using a hafnium oxide. In this way, mainly for the capacitors of 90-nm to 50-nm dynamic random access memories (DRAMs), high-k films such as hafnium oxide films or zirconium oxide films can be used as insulating films. As a method of forming a high-k film, there is an atomic layer deposition (ALD) method that has good concave part filling characteristics and step coverage.
In the process of forming a hafnium oxide film or zirconium oxide film, an amide compound such as tetra ethyl methyl amino hafnium (TEMAH: Hf[N(CH3)(C2H5)]4) or tetra ethyl methyl amino zirconium (TEMAZ: Zr[N(CH3) (C2H5)]4) is widely used as a metal source. H2O or O3 can be used as an oxidant, and recently O3 is more widely used as an oxidant because better film characteristics can be obtained. In an ALD film forming method, a metal source such as TEMAH or TEMAZ, and an oxidant such as O3 are alternately supplied to a reaction chamber to form a film.    [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2005-259966    [Patent Document 2] Japanese Unexamined Patent Application Publication No. 2006-66587
However, when forming capacitors in 50 or less nanometer DRAM devices, if a hafnium oxide film or silicon oxide film is formed by a film forming method of the related art, it is necessary to increase the size of electrodes due to a low dielectric constant, which makes the process more difficult to implement. As a result, throughput may be decreased or source material consumption may be increased to consequently increase manufacturing costs and cost of ownership (CoO: manufacturing costs per substrate). Relevant examples of the related art are disclosed in Patent Documents 1 and 2.